KR20240042100A - Variable height slanted grating method - Google Patents

Abstract

A device having a lattice structure and a method for forming the same are disclosed. The lattice structure includes forming recesses in the lattice layer. A plurality of channels are formed in the grid layer to define inclined grid structures in the grid layer. Recessed and inclined lattice structures are formed using a selective etch process.

Description

VARIABLE HEIGHT SLANTED GRATING METHOD

Embodiments of the present disclosure relate generally to methods and devices for use in display devices. More specifically, the present disclosure relates to grating structures for use in waveguides.

Virtual reality is generally considered to be a computer-generated simulated environment in which the user has an apparent physical presence. Virtual reality experiences are created in 3D and viewed using a head-mounted display (HMD), such as glasses or other wearable display devices with near-eye display panels as lenses to display a virtual environment that replaces the real environment. You can lose.

However, augmented reality allows an experience in which a user can still see the real surroundings through the display lenses of glasses or another HMD device while also seeing images of virtual objects that are generated and appear on the display as part of the real environment. Augmented reality may include any type of input, such as audio and tactile inputs, as well as virtual images and video that enhance or augment the environment the user experiences. As a cutting-edge technology, augmented reality presents many challenges and design constraints.

One such challenge is displaying a virtual image superimposed on the surrounding environment with sufficient clarity from various user viewpoints. For example, if the displayed virtual image and the user's eyes are not precisely aligned, the user may see a distorted and unclear image or may not be able to see the image completely. Moreover, the image may be blurry and may have a lower than desirable resolution at non-optimal viewing angles.

Accordingly, a need exists for improved methods of manufacturing augmented reality display devices.

This disclosure generally relates to methods and devices for use in display devices. More specifically, the present disclosure relates to grating structures for use in waveguides.

In one embodiment, a structure for use in a waveguide is provided. The structure has a substrate with a grid layer on top. A recess having a first end and a second end is formed in the grid layer. The recess has a depth that varies from the first end to the second end. A plurality of channels are formed in the grid layer. Each channel partially defines a portion of a plurality of lattice structures. The plurality of lattice structures also have depth changes from the first end to the second end defined by the recess.

In another embodiment, a structure for use in a waveguide is provided. The structure includes a substrate with a grid layer on top. Recesses are formed in the grid layer in the first and second directions. The recess has a depth that varies in the first and second directions, defining a three-dimensional shape. A plurality of channels are formed in the grid layer. Each channel partially defines a portion of a plurality of lattice structures. The plurality of lattice structures also have a depth that varies in the first and second directions as defined by the recess.

In another embodiment, a method of forming a lattice structure is provided. The method includes forming a recess in the grid layer, forming a hardmask and a photoresist stack over the grid layer, etching the photoresist stack, and forming a plurality of grid structures in the grid layer. Includes.

In such a way that the above-mentioned features of the present disclosure can be understood in detail, a more specific description of the present disclosure briefly summarized above may be made with reference to the embodiments, some of which are shown in the accompanying drawings. It is exemplified in the fields. However, it should be noted that the accompanying drawings illustrate exemplary embodiments only and should not be regarded as limiting their scope, since the present disclosure is capable of other equally effective embodiments.
1 is a schematic cross-sectional view of a display device according to an embodiment described herein.
2 is an enlarged cross-sectional view of a portion of a waveguide with a wedge-shaped recessed structure formed therein, according to one embodiment described herein.
FIG. 3 is an enlarged cross-sectional view of the waveguide of FIG. 2 with a photoresist laminate formed thereon.
FIG. 4 is an enlarged cross-sectional view of the waveguide of FIG. 3 with a patterned hard mask formed on the top.
FIG. 5 is an enlarged cross-sectional view of the waveguide of FIG. 4 with lattice structures formed therein.
6 is a flow diagram of a method of manufacturing a waveguide, according to one embodiment described herein.
7A-7C are enlarged cross-sectional views of examples of recessed structural shapes according to embodiments described herein.
8A-8C are perspective views of examples of three-dimensional shapes of a recessed structure according to embodiments described herein.
To facilitate understanding, identical reference numbers have been used where possible to designate identical elements that are common to the drawings. It is contemplated that elements and features of one embodiment may be beneficially incorporated into other embodiments without further recitation.

A device having a lattice structure and a method for forming the lattice structure are disclosed. The lattice structure includes recesses within the lattice layers. A plurality of channels are formed in the grid layer to define inclined grid structures in the grid layer. Recessed and inclined lattice structures are formed using a selective etch process.

Figure 1 is a schematic cross-sectional view of the waveguide 104 implemented in the display device 100. Display device 100 is configured for augmented, virtual, and mixed or merged reality applications as well as other display applications, such as handheld display devices.

The display device 100 uses a waveguide ( 104). When implemented in display device 100 , first surface 122 of waveguide 104 is positioned adjacent to and facing the user's eye 111 . The second surface 124 of the waveguide 104 is disposed opposite the first surface 122 and adjacent to and facing the surrounding environment 130 . Although illustrated as flat, it is contemplated that waveguide 104 may be curved or angular depending on the desired application.

The display device 100 further includes an image microdisplay 128 for directing the light beams 120 of the generated virtual image to the waveguide 104 . Light beams 120 of the virtual image propagate in waveguide 104 . Generally, waveguide 104 includes an input coupling region 106, a waveguide region 108, and an output coupling region 110. Input coupling region 106 receives light beams 120 (virtual image) from image microdisplay 128 and light beams 120 travel through waveguide region 108 to output combining region 110, where , the user's viewpoint 101 and field of view enable visualization of a virtual image superimposed on the surrounding environment 130 . Image microdisplay 128 is a high-resolution display generator, such as a liquid crystal on silicon microdisplay, that projects light beams 120 of a virtual image onto a waveguide 104.

Waveguide 104 includes input grating structures 112 and output grating structures 114 . Input grating structures 112 are formed on waveguide 104 in the area corresponding to input coupling region 106 . Output grating structures 114 are formed on waveguide 104 in the area corresponding to output coupling region 110 . Input grating structures 112 and output grating structures 114 affect light propagation within waveguide 104. For example, the input grating structure 112 couples in light, such as light beams 120, from the image microdisplay 128, and the output grating structure couples the light to the user's eyes 111. out).

For example, the input grid structures 112 affect the field of view of the virtual image displayed to the user's eyes 111. Output grating structures 114 affect the amount of light beams 120 that are collected and ejected from the waveguide 104 . Additionally, the output grating structures 114 modulate the field of view of the virtual image from the user's viewpoint 101 and increase the viewing angle at which the user can view the virtual image from the image microdisplay 128. In another example, a grating structure (not shown) is also formed in the waveguide region 108 between the input coupling region 106 and the output coupling region 110. Additionally, multiple waveguides 104 each having desired grid structures formed therein may be used to form the display device 100.

Figure 2 is an enlarged partial cross-section of the waveguide 200 for forming grating structures 280 (Figure 5) therein. In this example, waveguide 200 has a substrate 202 with an etch stop layer 204 formed thereon. Substrate 202 is made of an optically transparent material, such as silicon. An etch stop layer 204 is formed over the substrate 202 . The etch stop layer 204 is formed by, for example, a chemical vapor deposition (CVD) process, a physical vapor deposition (PVD) process, or a spin-on process. Etch stop layer 204 is formed of a material that is resistant to etching processes, such as titanium nitride or tantalum nitride, among others.

A grid layer 206 is formed over the etch stop layer 204. Grating layer 206 is formed of an optically transparent material. In one example, grating layer 206 is formed of a silicon-based material, such as silicon nitride or silicon oxide, or a titanium-based material, such as titanium oxide. The material of the grating layer 206 has a high refractive index, such as about 1.3 or higher, such as 1.5 or even higher. Typically, the grating layer 206 has a thickness of less than about 1 micrometer, such as about 150 nm to about 700 nm. For example, the grating layer 206 has a thickness of about 200 nm to about 600 nm, such as about 300 nm to about 500 nm, such as about 400 nm.

After the grid layer 206 is formed, a recess 220 is formed in the grid layer. Recess 220 may be any suitable recessed structure and shape, including, but not limited to, wedge-shaped shapes, cone-shaped shapes, conical shapes, etc. As shown in FIG. 2 , the recess 220 has a flat trapezoid wedge-shaped structure with a length L between the first end 230 and the second end 232 . The depth D of recess 220 increases from first end 230 to second end 232 . That is, the depth D of the recess 220 is minimum at the first end 230 and maximum at the second end 232. The depth (D) is in the range of about 0 nm to about 700 nm, such as about 100 nm to about 600 nm, such as about 200 nm to about 500 nm. For example, the depth D is about 300 nm to about 400 nm, such as about 350 nm. In the embodiment of Figure 2, the length L is substantially larger compared to the depth D. For example, the length L is about 25 mm, while the depth D at the first end 230 is about 0 nm to about 50 nm and the depth D at the second end 232 is about 250 nm. to about 700 nm. Accordingly, recess 220 has an angle ( ) has a substantially shallow slope, shown as ). In this example, the angle ( ) is less than 1 degree, such as less than 0.1 degree, such as about 0.0005 degree. The slope of the recess 220 is exaggerated for clarity ( ) is exemplified herein.

In one example, recess 220 is formed by selectively etching regions of grid layer 206. For example, first portion 220a of recess 220 is formed by etching grating layer 206 at a low etch rate and/or low power. Second portion 220b is formed by etching grating layer 206 at an increased etch rate and/or power than portion 220a. Similarly, third portion 220c is formed by etching grating layer 206 at a higher etch rate and/or power than portions 220a and 220b. Here, three parts are used for illustration purposes. However, any desired number of portions may be used to form recess 220 and etched in a single operational step or in multiple steps. Additionally, etching may occur at gently increasing intervals (i.e., etch rate and/or power) such that recess 220 has a smooth surface. In one example, the area for grating structures 280 is defined prior to formation of recess 220, such as by using a mask (eg, a photolithographic mask or proximity mask) or an etch beam. Forming the recess 220 with a smooth outline improves image quality by better controlling the diffraction and projection of light beams compared to a rough (i.e. stepped, etc.) structure. Accordingly, the power of light extracted across the grating structures 280 is significantly more uniform.

Figure 3 is a cross-section of the waveguide 200 with the photoresist laminate 250 formed on the top. A shape-following hardmask 208 is formed over the grid layer 206. Hardmask 208 is formed of titanium nitride using, for example, a chemical vapor deposition process. In one example, hardmask 208 has a thickness of about 30 nm to about 50 nm, such as about 35 nm to about 45 nm. The photoresist stack 250 includes a back anti-reflective coating (BARC) 210, a silicon anti-reflective coating (SiARC) 212, and a photoresist 214. BARC 210 is formed using a spin-on process such that top surface 210a of BARC 210 is substantially flat (i.e., parallel to surface 202a of substrate 202). By forming BARC 210 using a spin-on process, there is no need for an etch process or polishing process to planarize BARC 210, which may overeat BARC 210 and/or underlying lattice layer 206. Eliminates the potential for harm or harm.

Next, SiARC 212 is formed on BARC 210. SiARC 212 is formed from a silicon-based material using, for example, a chemical vapor deposition process or a spin-on process. Photoresist 214 is formed over SiARC 212. Photoresist 214 is formed from a polymeric material using, for example, a lithography process. In one example, photoresist 214 is formed by exposing one or more grating lines and developing photoresist 214 using spin-on coating. After formation of photoresist 214, photoresist stack 250 is patterned using an etch process. It is understood that patterning with BARC 210 and SiARC 212 is an exemplary method. Other methods of patterning may be used with the present disclosure. The patterning method is generally selected with respect to the size and shape of the structure to be patterned.

FIG. 4 is a cross-section of the waveguide 200 after etching and removal of the photoresist stack 250 of FIG. 3 . Etching the photoresist stack 250 patterns the hardmask 208 as shown in FIG. 4 . The hardmask 208 functions as a pattern guide for the formation of the inclined grid structures 280 shown in FIG. 5 . Inclined grid structures 280 are defined between one or more channels 270 formed within grid layer 206. To form channels 270, grating layer 206 is etched again using a selective etch process. In one example, the inclined lattice structures 280 are formed using a process similar to the process utilized to form the wedge-shaped recess 220, but with the sequence reversed. For example, the area corresponding to the third portion 220c is etched at a low etch rate and/or low power. The area corresponding to the second portion 220b is etched at a higher etch rate and/or power than the third portion 220c. The area corresponding to the first portion 220a is etched at a higher etch rate and/or power than the portions 220b and 220c. In one example, etch stop layer 204 is etched to improve the definition of sloped lattice structures 280. After the inclined grid structures 280 are formed, the hardmask 208 is optionally removed using an etch process.

Each inclined grid structure 280 having a depth d is formed. For example, the inclined grating structures 280 may have a depth d of about 5 nm to about 700 nm, such as about 100 nm to about 600 nm, such as about 500 nm. The depth of the inclined grating structures 280 is selected depending on the desired wavelengths (i.e., color) for projection of the image to the user. In the embodiment of Figure 5, the depth d of the inclined lattice structures decreases from the first end 230 to the second end 232 of the recess 220 (shown virtually). The upper surfaces 280a of each inclined lattice structure 280 define an angled plane 290 corresponding to the slope of the recess 220 . Additionally, each inclined lattice structure 280 has an angle ( ) can have. Angle( ) is, for example, from about 0 degrees to about 70 degrees, such as from about 25 degrees to about 45 degrees, such as about 35 degrees. By forming inclined grating structures 280 as described herein, the clarity of the image projected by waveguide 200 is substantially improved due to improved diffraction and projection of light toward the desired image plane. By controlling the shape of the tilted grating structures 280, changes in diffraction of different wavelengths (i.e., different colors) are controlled to improve image quality. Due to the increased control provided by the inclined grating structures 280, optical efficiency (i.e., projection of desired wavelengths to the user's viewpoint) is greatly improved. Additionally, projection of unwanted wavelengths is reduced, thereby increasing the clarity and quality of the projected image.

2-5, recess 220 is shown as having a flat trapezoid wedge shape. However, the etching process described herein advantageously allows recess 220 to have a slope and/or curvature in one or more directions. Accordingly, recess 220 may have any suitable shape as described above. 7A-7C illustrate other examples of shapes that may be used for recess 220. For example, Figure 7A illustrates a substantially isosceles triangular recess 720 in the grating layer 706 of the waveguide 700. Recess 720 has two flat, sloping portions extending from respective peripheral regions 720a, 720b toward central region 720c. 7B illustrates another recess 750 in the grating layer 736 of waveguide 730. The recess 750 has a curved concave structure with a shallow depth D in the peripheral regions 750a, 750b and an increased depth in the central region 750c. In one example, recess 750 has a parabolic shape. For example, depth D increases non-linearly from peripheral regions 750a, 750b to central region 750c. FIG. 7C illustrates another recess 780 in the grating layer 766 of the waveguide 760. Recess 780 has a depth D that oscillates from first end 780a to second end 780b, thereby forming a pattern of periodic depths D for recess 780. . Recess 780 is shown as linear sawtooth oscillations of depth D. However, it is contemplated that depth D may vary non-linearly such that recess 220 has wavy oscillations of depth D. The depth D of the recess, such as recesses 720, 750, and 780, is its length from the first end (i.e., 720a, 750a, 780a) to the second end (i.e., 720b, 750b, 780b). It may vary linearly or non-linearly across (L).

In another example, recess 220 has a three-dimensional shape. That is, the depth varies in more than one direction, such as two directions (i.e., a first direction (X) and a second direction (Y)), as illustrated in the examples of FIGS. 8A-8C. Figure 8A illustrates a recess 820 with a saddle point shaped curvature (i.e., hyperbolic paraboloid shape). FIG. 8B illustrates a recess 850 having an elliptical parabolic shape with positive curvature. Figure 8C illustrates a recess 880 having an elliptical parabolic shape with negative curvature. The three-dimensional shape of the recess is not limited to the examples in FIGS. 8A-8C. Other desired shapes, such as paraboloids, ellipsoids, and linearly inclined shapes of square domains with positive or negative curvature, among others, are also contemplated and may be used with the present disclosure. In these cases, the depth of the recess varies in both X and Y directions. Accordingly, the top surfaces of the inclined grid structures, such as top surfaces 280a in Figure 5, are curved as defined by the shape of the curvature of the recess. The shape and/or depth of the recess is not limited to variations in the X and Y directions. For example, the depth of the recess can vary in three directions, four directions, or even more directions. Additionally, although illustrated herein using a Cartesian coordinate system, the wedge-shaped structure may be formed using other coordinate systems, such as polar, cylindrical, or spherical coordinates. Embodiments herein can advantageously be used to form any desired shape for the recess.

6 is a flow diagram illustrating a method 600 for forming a grating structure, such as inclined grating structures 280, in a waveguide. The waveguide is generally formed on a substrate. In one example, the substrate is a silicon-based glass substrate with an optional etch stop layer and a grid layer formed thereon. In another example, the substrate is a glass substrate without an etch stop layer. In such cases, the substrate functions as a lattice layer, and lattice structures are formed directly in the substrate. At operation 602, a recess is formed in the grid layer over the random etch stop layer. In one example, the recess is formed using an etch process that selectively treats regions of the substrate as described above. In operation 604, a shape-following hardmask is deposited on the grid layer. A photoresist stack including a back anti-reflective coating (BARC), a silicon anti-reflective coating (SiARC), and a photoresist is formed over the hardmask. The back anti-reflective coating is formed using spin-on techniques such that the top surface of the layer is substantially flat.

In operation 606, the photoresist stack is etched to form the desired pattern on the hardmask. At operation 608, the hardmask and grating layer are etched using a selective etch process to form grating structures in the grating layer as described above. In operation 610, the etch stop layer, if present, is optionally etched to improve definition of the shape of the lattice structures. In operation 612, the hardmask is optionally removed, such as using an etch process.

By utilizing the embodiments described herein, a waveguide with inclined grating structures is formed. The inclined grating structures improve the function of the waveguide by better collecting and directing light through the waveguide, thereby improving the clarity of the projected image. Inclined grating structures provide increased control over the wavelengths of light projected onto the desired image plane. The uniformity of power of light ejected by the waveguide is significantly more uniform. Embodiments described herein further improve the manufacturing of waveguides by eliminating manufacturing processes, such as mechanical polishing, that can damage the layers used to form the waveguide. Additionally, embodiments described herein allow the grating to have a two-dimensional or three-dimensional shape, which allows the use of the waveguide in an increased range of applications.

Although the foregoing relates to embodiments of the disclosure, other and additional embodiments of the disclosure can be devised without departing from the basic scope of the disclosure, and the scope of the disclosure is defined in the claims below. is determined by

Claims (20)

As an optical device,
a substrate, on which an optically transparent grid layer is disposed;
a recess formed in the grid layer, the recess having a depth that varies from a first end of the recess to a second end of the recess; and
a plurality of inclined grid structures formed in the grid layer below the recess and partially defining a portion of the recess, the depth of the plurality of inclined grid structures varying from the first end to the second end, The angle of each of the plurality of inclined lattice structures with respect to a plane perpendicular to the substrate is 25 degrees to 45 degrees.
An optical device comprising: The optical device of claim 1, wherein the recess has a planar and scalene wedge-like shape. 3. The optical device of claim 2, wherein upper surfaces of the plurality of inclined grating structures are coplanar. 4. The optical device of claim 3, wherein the depth of the plurality of inclined grating structures varies linearly from the first end to the second end. The optical device of claim 1, wherein the recess has a frustum-like or conical shape. 6. The optical device of claim 5, wherein upper surfaces of the plurality of inclined grating structures define a curvature. 7. The optical device of claim 6, wherein the depth of the plurality of inclined grating structures varies non-linearly from the first end to the second end. 2. The optical device of claim 1, wherein the recess has a triangular shape. 2. The optical device of claim 1, wherein the recess has an oscillating depth. As an optical device,
a substrate, on which an optically transparent grid layer is disposed;
a recess formed in the grid layer, the recess having a depth that varies in a first direction and a second direction to define a three-dimensional shape; and
a plurality of inclined grid structures formed in the grid layer below the recess and partially defining a portion of the recess, the depth of the plurality of inclined grid structures varying in the first direction and the second direction, The angle of each of the plurality of inclined lattice structures with respect to a plane perpendicular to the substrate is 25 degrees to 45 degrees.
An optical device comprising: 11. The optical device of claim 10, wherein the recess has a parabolic shape. 12. The optical device of claim 11, wherein the recess has a hyperbolic paraboloid shape. 12. The optical device of claim 11, wherein the recess has an elliptical parabolic shape. 11. The optical device of claim 10, wherein the recess has a negative curvature. 11. The optical device of claim 10, wherein the recess has a positive curvature. A method of forming an optical device, comprising:
forming an optically transparent grid layer over the substrate, the grid layer comprising a silicon-based or titanium-based material and having a thickness of less than 1 μm;
forming a recess in the grid layer by selectively etching the grid layer, the recess having a depth that varies from a first end of the recess to a second end of the recess;
depositing a shape-following hardmask on the grid layer;
forming a photoresist stack over the shape-following hardmask, the photoresist stack comprising a back antireflective coating (BARC), a silicon antireflective coating (SiARC), and a photoresist;
forming a desired pattern on the hard mask by etching the photoresist laminate; and
Selectively etching the hard mask and the grid layer to form inclined grid structures in the grid layer.
How to include . According to clause 16,
forming an etch stop layer on the substrate prior to forming the grid layer, wherein the etch stop layer is formed by a chemical vapor deposition (CVD) process, a physical vapor deposition (PVD) process, or a spin-on process. How to include it. 17. The method of claim 16, wherein the BARC is formed by a spin-on process and the SiARC is formed by a CVD process or a spin-on process. 17. The method of claim 16, wherein the recess has a wedge-like, frustum-like, or conical shape. 17. The method of claim 16, wherein the recess has a three-dimensional parabolic shape.

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